Cross section image of the device. To make it, dig a 1 block deep hole and place your furnace inside. (to get the custom name, rename the furnace to whatever you want in an anvil) Shift-right click with a flint and steel to light the top of the furnace. (Note: It is very important that you set the gamerule doFireTick to false for this to work. to set this, open up the command prompt and type in /gamerule doFireTick false)